Following the referendum campaign I have written to my trade union to opt out of their political fund. Some unions have options like putting this part of the membership subscription into general campaigning or welfare funds, but Unite only seems to have the option of giving it to the Labour Party. As I am not a supporter of the labour Party I don't see any reason to continue doing that. If you would like to do the same you will find the form here. Just fill it in and give to your branch secretary.